FIG. 1 shows a subset of the arterial vascular system of a subject 102 in need of a stent, and for clarity in understanding the issues related to guiding the stent into a human patient, the venous system, organs, pulmonary arteries and veins, and many branches of the circulatory system are not shown. Heart 104 pumps oxygenated blood through the aortic arch 106, which guides upward-flowing blood from the heart to a downward flow for delivery to the lower organs and right femoral artery 120 and left femoral artery 122, which are interchangeably used for stent arterial access, as will be described later. Many variations in the vessels formed in a subject are found from one subject to another, and the particular subject 102 shown in FIG. 1 has an aortic arch 106 with three major branching vessels which leave the aortic arch, including a first branching vessel which forms the left subclavian artery (LSA) 114 and left vertebral artery (LVA) 116, a second branching vessel which forms the left common carotid artery 118 (LCCA), and a third branching vessel which forms the right subclavian artery (RSA) 108, right vertebral artery (RVA) 110, and right common carotid artery (RCCA) 112.
Arteriosclerotic disease processes known as Atherosclerosis often afflict the arterial system, and the affected areas include the aortic arch 106, left common carotid artery 118 (branching to internal carotid artery 119 and external carotid artery 121), and right common carotid artery 112 (which also branch to internal and external carotid arteries, not shown). The disease processes which take place in these vessels cause deterioration of the interior vessel walls, and diseased material which detaches from the interior vessels can be swept through the arterial system with successively decreasing vessel diameter until it becomes lodged in a vessel constriction, causing the cessation of blood flow in the blocked area, leading to tissue death from loss of oxygenation. This disease process is the leading cause of strokes, heart attacks, and other debilitating or fatal events. When a subject presents with this disease process, a variety of imaging techniques may be used to ascertain the nature of the blockage or potential blockage, using contrast agents and x-ray or magnetic resonance (MR) imaging, including computerized axial tomography (CAT) scans, whereby the imaging contrast agent provides increased differentiation between the vessel walls and the blood flowing through the vessel.
As atherosclerosis in the carotid artery progresses, the risk of stroke increases, and it becomes necessary to intervene to prevent stroke or death from clots or vessel debris which becomes lodged in the brain, specifically related to disease of the internal carotid artery branch which serves the brain, or the common carotid artery which precedes it in the circulatory path. It should be noted that stroke is the third leading cause of death in the developed nations. 85% of all strokes are ischemic (due to brain circulation compromise) in nature and 20-30% of all ischemic strokes are caused by carotid artery atherosclerotic occlusive disease. For atherosclerotic occlusive disease of the internal or common carotid artery, one procedure performed by interventionalists (interventional radiologists, vascular surgeons, or interventional cardiologists) is the installation of a stent, which is an expanding cylindrical wire or plastic mesh which supports and stabilizes the diseased area of the artery, and reduces the stenosis (narrowing) of the artery through a treatment known as angioplasty, whereby an inflatable balloon is used to momentarily expand the stent across the inner diameter of the vessel in the stenotic region.
The prior art installation of a carotid artery stent described for FIG. 1 is done in a series of steps for which the order of the steps and types of equipment may vary. As will be described, the types of interventional devices which are used in the procedures include a small diameter guidewire which may be co-inserted with a small catheter, a subsequently inserted stiff guidewire which may be co-inserted or replace the small diameter guidewire in the small catheter, a sleeve or sheath which may be threaded over the small catheter, and an angioplasty catheter which may be threaded over the small catheter or exchanged for the small catheter during the procedure. For clarity, FIG. 1 broadly indicates the path 135 used by interventional devices in the example (where the interventional devices may represent any of the previously described devices in any combination and achieving an insertion level which is typically less than the entire path length 135, which extends to the ultimate treatment region 136 reached by the stent catheter.
Following FIG. 1, the first step of a stenting procedure involves threading the small diameter guidewire, which may be a 0.035 inch diameter steerable guidewire having a bent tip, where the tip may also be hydrophilic) through a steerable catheter which may also have a bent tip for steering. Examples of such steerable catheter guidewires are Berenstein or Vertebral with trade names H1H or Headhunter) or reverse curve (Simmons or Vitek). Steering is done by rotating the guidewire, which causes the bent tip to select the desired artery and follow that arterial path with the catheter following and assisting in selection. The first step therefore is the installation at percutaneous location 132 of a femoral artery (FA) catheter, which is usually 4 to 6 French diameter, and guided into the femoral artery through the aortic arch 106 and to the common carotid artery 118. The guidewire is fed from a sterile drape 130 which furnishes the approximately 260 cm of length required. The external carotid artery (ECA) 121 is then selected often with the angled FA catheter and same guidewire followed by selection of an external carotid artery branch while the guidewire is advanced.
Navigational information on the progress of the guidewire is provided by a radiographic display which is used in combination with arterial contrast agents which delineate the vessel walls with respect to the guidewire. One typical imaging system is x-ray fluoroscopy, whereby a source of x-rays is applied in one or more planes through the patient to a 2D or 3D detector, and the real-time radiographic images are used by the interventionalist to provide guidance information. The small diameter guidewire inside the catheter is then replaced with a stiff guidewire (to eventually support the subsequently placed long guiding sleeve or sheath). The small diameter catheter may or may not be removed at this point leaving the stiff guidewire in place. The long guiding sleeve or sheath (6 to 8 French) is then advanced over the stiff guidewire alone (or over the catheter and stiff guidewire combination) from the femoral access through the descending aorta region 134 and through the aortic arch region 106 to the distal common carotid artery 118 just below the bifurcation. Contrast injection is performed through the guiding sleeve or sheath to now visualize the internal carotid artery 119 and external carotid artery 121. The stiff guidewire in the ECA 121 is typically removed at this point. The stenosis in the internal carotid artery (ICA) 119 is gently traversed with a 0.014 inch guidewire tip fixed embolic protection device (EPD), examples of which are manufactured under the trade names Accunet or Filterwire, versus a embolic protection device that is separately deployed over a 0.014 inch guidewire with a 0.017 inch tip, such as those with trade names Nav6 or Emboshield. The EPD is deployed within the distal portion of the cervical segment of the ICA 119. An angioplasty balloon catheter is then threaded through the sheath over the guidewire portion of the EPD to the location of the stenosis 136 to then predilate the stenosis. The angioplasty catheter is then exchanged for a stent delivery catheter which has a self expanding stent at the distal end, which is guided to the site of the stenosis 136 shown in FIG. 1. A slightly larger angioplasty balloon catheter is then used to postdilate the stent to the desired diameter. Carotid and cerebral angiography is then perform to confirm an adequate result.
The critical part of steering occurs when selecting the particular vessel of the aortic arch shown in FIG. 1. Each subject 102 undergoing the procedure may have a different aortic arch vascular configuration. FIG. 1 shows a common arrangement of vessels at the aortic arch, as was previously described, and the radiographic contrast agent is injected to delineate the vessel outlines, which enables the interventionalist to select and steer into the vessel which leads to the desired carotid artery, shown as the left internal carotid artery 119 with the expanding stent on the distal end of the stent delivery catheter, which was introduced after the angioplasty catheter as previously described. The stent may be a wire or plastic mesh which is guided into place and affixed by inflating a balloon which deforms the stent to conform to the inner diameter of the blood vessel. Many variations in the arrangement of arteries which branch from the aortic arch may be present, and are classified according to “type” where the type number signifies the extent of vertical deviation (or slope) of the bifurcation point for arteries which branch at the top of the aortic arch. FIG. 1 shows three arteries which branch from the top of the aortic arch 106 in substantially the same horizontal plane, and is known as a “type 1” aortic arch. A “type 2” aortic arch has one of the branching arteries located 1-2 common carotid artery diameters below the topmost, and a “type 3” aortic arch has a separation from horizontal of more than 2 common carotid artery diameters. Since the stent delivery catheter is advanced from the descending aorta region 134 to the top of the aortic arch 106, the type number provides an indication of how difficult the navigation to the common carotid artery will be according to the extent to which the catheter must change direction to guide into the common carotid artery, as will be described. As can be seen from FIG. 1, the long guiding sleeve or sheath can be guided into the left common carotid artery 118 without significant changes in direction along the path. The long guiding sleeve or sheath is typically placed in the common carotid artery 118 just below the bifurcation point for the external carotid artery 121 and internal carotid artery 119, after which the angioplasty catheter and stent delivery catheter are guided into the desired artery such as the internal carotid artery 119 as shown in FIG. 1.
FIG. 2A shows a magnified view of an aortic arch region 202 variation from 106 of FIG. 1, where the subject of FIG. 2A has a type II aortic arch variation (branching artery 211 is 1-2 carotid artery diameters below the first branch 204 indicated by distance 209) in vascular configuration and also a branch point for the LCCA 206 above second branch 211, known collectively as a type II-A Bovine aortic arch 208, which is distinguishable from FIG. 1 having three branches at the top of the aortic arch. The type II-A Bovine aortic arch has only two branches 204 and 211 at the top of the aortic arch, with the left common carotid artery 206 not having its own vessel leading to the aortic arch (as was the case in FIG. 1), but instead branching off from second branch 211 which also forms the right common carotid artery 214, right vertebral artery 212, and right subclavian artery 210. One difficulty that can be seen from the LCCA 206 geometry of FIG. 2A is that the initial guidewire entry into the LCCA from the aortic arch 202 is a sharp turn in a vessel transitioning from the large diameter aortic arch 202 to the much smaller diameter LCCA 206, and additionally with a sharp angle of approach and difficult catheter guidance. This type of Bovine aortic arch can be difficult to navigate without insult or injury to the adjacent inner walls of the aorta, which are likely to also have atherosclerosis as the region to be treated by angioplasty, and this agitation during guidance may cause diseased vessel material to break loose and cause a stroke during the installation of the stent—which original purpose was to reduce such risk. Blood vessels which present these risks associated with atherosclerosis and with difficult entry geometry are known as hostile vessels, and accordingly, the aortic arch of FIG. 2A is known as a hostile aortic arch, with the aortic arch type classification indicating the level of difficulty and type of difficulty for FA catheter guidance to the carotid artery.
It is desired to provide an apparatus and method for installation of a carotid artery stent which eases the navigation of the guidewire through hostile vessels of the aortic arch, thereby reducing patient risk and procedure length, and accordingly increasing patient safety.
It is also desired to provide an apparatus and method for through-and-through access and guidance through tortuous vessels by using a major vessel for entry of a catheter into a large vessel in combination with the entry of a guidewire into a minor surface vessel, the apparatus and method for use with or without a multi-plane imaging device for navigating the tortuous vessel region.